Loud and Strange noise from AC

[dobx]

I have the factory AC system in the GTR, and it has been working fine for years. However, in the past week, I noticed that it makes a very loud noise when the AC kicks on. The noise comes from the in-dash unit. There is no noise in the engine bay. This noise sounds like the shrieky noise of a lose fan belt. The shriek only lasts for a quick second every time the AC turns on, and it is very loud. The car also jerks a little (while moving) when this happens. The shriek seems not to happen when the car is in neutral while stopped. AC still blows cold.

Anyone knows what this problem is?

[60mph]

Could be a dry spindle bearing ; but I do not know the internals of the Ultima motor . Some motors have their spindles running in scintered bronze bearings soaked in oil . The oil can "go" and you have to lubricate with a syringe and pipe using engine oil which soaks into the bronze . You certainly get a scream when the motor starts and it would have less resistance to current at this point which explain your engines hesitancy due to greater pull on the alternator belt . Guesswork but try getting to the spindle bearings .

Frank

[Steve_D]

Are you sure it is not the drive belt?

As others have had mount failures with alternators in the past I run all my belts as slack as I dare and the sound you describe is exactly what I get when my AC kicks in and the belt momentarily slips.

If it is the fan motor then I wish you luck getting at it to lube the bearings.

Steve

[UltimaCH]

If its coming from the in-dash unit, could be a dry bearing.

[dobx]

Steve_D said:

Are you sure it is not the drive belt?

As others have had mount failures with alternators in the past I run all my belts as slack as I dare and the sound you describe is exactly what I get when my AC kicks in and the belt momentarily slips.

If it is the fan motor then I wish you luck getting at it to lube the bearings.

Steve

I am sure it is not the drive belt. The shriek is from the AC unit inside the cabin. Another odd thing is that this noise does not happen when the car is idling. It seems to happen when rpm is above 2000.

What is the easiest way to get to it to lube the bearings?

[Steve_D]

dobx said:

What is the easiest way to get to it to lube the bearings?

First thing to check is the ends of the fan housing. I seem to remember that someone had the grill in the end of the housing come adrift and it jambing in the fan so this may be your squeal.

The motor has a fan on each end, I believe the motor/fans are trapped between two halves of the plastic housing. I don't think you can remove the whole assembly because it won't go past the chassis rails etc but you may be able to open the housing to remove the motor/fans assembly.

Also wait for others to advise as some have retro fitted AC and may be able to offer better advise.

Steve

Edited by Steve_D on Monday 24th August 19:47

Edited by Steve_D on Monday 24th August 22:50

[GTRMikie]

dobx said:

I am sure it is not the drive belt. The shriek is from the AC unit inside the cabin. Another odd thing is that this noise does not happen when the car is idling. It seems to happen when rpm is above 2000.

I can't see any possible connection between engine speed and the AC fan bearings, apart from maybe the alternator/battery not providing enough power at low revs to spin the fan at "shrieking speed" Does the fan run at a lower speed when the engine is idling?

[dobx]

GTRMikie said:

dobx said:

I am sure it is not the drive belt. The shriek is from the AC unit inside the cabin. Another odd thing is that this noise does not happen when the car is idling. It seems to happen when rpm is above 2000.

I can't see any possible connection between engine speed and the AC fan bearings, apart from maybe the alternator/battery not providing enough power at low revs to spin the fan at "shrieking speed" Does the fan run at a lower speed when the engine is idling?

I think the fan runs at the same speed when the engine is idling, but you brought up a good point. I will check the fan speed when engine is idling. Also, there is no shriek if just the fan is turned on. The shriek only comes on when AC kicks on.

[Steve_D]

dobx said:

The shriek only comes on when AC kicks on.

Try it with the fan at its lowest and highest speeds. If shriek is the same then I would suspect the valve on the AC unit doing the same sort of thing you get in a domestic water system where it manifests as a knock rather than a shriek due to the lower pressure.

Steve

[dobx]

60mph said:

Could be a dry spindle bearing ; but I do not know the internals of the Ultima motor . Some motors have their spindles running in scintered bronze bearings soaked in oil . The oil can "go" and you have to lubricate with a syringe and pipe using engine oil which soaks into the bronze . You certainly get a scream when the motor starts and it would have less resistance to current at this point which explain your engines hesitancy due to greater pull on the alternator belt . Guesswork but try getting to the spindle bearings .

Frank

I got the problem sorted out. The lubing fixed the problem. Thank you all for your input and advice.